Good thing about Crucial is if you order it via their configurator (vs ordering it from say NewEgg) then it is guaranteed to work in the system you ordered it for. I have had one instance where Kingston RAM wouldn't work in a Dell (but worked fine in another laptop). But, agree, both are high quality.

From my experience, Crucial has offered me a slightly better service overall. The delivery on all the crucial RAM I have purchased have been next day, while the RAM I purchased from Kingston took a bit longer to deliver (most likely the retailer's fault, since I usually purchase Crucial RAM off Crucial's own own website, while Kingston relies on retailers, and some retailers aren't very good when it comes to delivery).